diff --git a/src/js/net/minecraft/client/gui/screens/GuiCreateWorld.js b/src/js/net/minecraft/client/gui/screens/GuiCreateWorld.js
index a0a8252..0988e05 100644
--- a/src/js/net/minecraft/client/gui/screens/GuiCreateWorld.js
+++ b/src/js/net/minecraft/client/gui/screens/GuiCreateWorld.js
@@ -26,7 +26,7 @@ export default class GuiCreateWorld extends GuiScreen {
             let seed = this.fieldSeed.getText();
             if (seed.length === 0) {
                 seed = new Random().nextLong();
-            } else if (typeof seed === "string") {
+            } else if (isNaN(seed)) {
                 let h = 0;
                 for (let i = 0; i < seed.length; i++) {
                     h = 31 * h + seed.charCodeAt(i);